as in treacherous
formal
causing harm in a way that is gradual or not easily noticed
Most people with this insidious disease have no idea that they are infected. an insidious enemy
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Recent Examples of insidious
The show, which runs through March 28, has a blistering message to impart about the insidious nature of authoritarian political movements and the dangers of being oblivious or indifferent.
—
Christopher Arnott, Hartford Courant, 18 Mar. 2026
But the kind of harassment that may not rise to the level of a crime in most countries – more pervasive and more subtle, but nonetheless insidious – has largely remained unacknowledged in Brazilian jiu-jitsu.
—Ina Seethaler, The Conversation, 4 Mar. 2026
Moderate beauty, yet insidious.
—Literary Hub, 2 Mar. 2026
Now there is a new and arguably more insidious form of theatricality to be overcome, a greater threat to the illusionism that lies at the heart of Bove’s bent and colored steel sculptures.
—Gordon Hughes, Artforum, 1 Mar. 2026
See All Example Sentences for insidious
Christopher Arnott, Hartford Courant, 18 Mar. 2026
But the kind of harassment that may not rise to the level of a crime in most countries – more pervasive and more subtle, but nonetheless insidious – has largely remained unacknowledged in Brazilian jiu-jitsu.
—Ina Seethaler, The Conversation, 4 Mar. 2026
Moderate beauty, yet insidious.
—Literary Hub, 2 Mar. 2026
Now there is a new and arguably more insidious form of theatricality to be overcome, a greater threat to the illusionism that lies at the heart of Bove’s bent and colored steel sculptures.
—Gordon Hughes, Artforum, 1 Mar. 2026
See All Example Sentences for insidious
Recent Examples of Synonyms for insidious
Adjective
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That led to a treacherous trek to Germany, which became a near-death experience.—
Greg Riddle,
Dallas Morning News,
26 Mar. 2026
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For Prisoner, Rahim plays treacherous convict Tibor Stone, whose life is put in the hands of a young, principled prison officer Amber (Izuka Hoyle).—
Diana Lodderhose,
Deadline,
26 Mar. 2026
Adjective
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Another camera, an eye tuned to the subtle strangeness of an otherwise ordinary day—someone or something, somewhere, must have caught a glimmer of the truth.—
Vinson Cunningham,
New Yorker,
1 Apr. 2026
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Vice President Vance, who is considered an isolationist, expressed private skepticism ahead of the attacks, and his relative silence during the first weeks of the war was perceived as a subtle way of distancing himself from the conflict.—
Jonathan Lemire,
The Atlantic,
1 Apr. 2026
Adjective
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Lebohang Morake — the Grammy-winning South African composer behind the film’s opening Zulu vocals — filed a federal civil complaint in California on March 16 against the comedian, Learnmore Jonasi, alleging that the translation is false and damaging to his life’s work.—
Joe Kottke,
NBC news,
27 Mar. 2026
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Rebollo, a 58-year-old Chula Vista resident, pleaded guilty in December in San Diego federal court to one count of wire fraud conspiracy, one count of filing a false tax return and one count related to Social Security fraud.—
Alex Riggins,
San Diego Union-Tribune,
27 Mar. 2026
Adjective
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Also, offering free samples is deceptive marketing, due to evidence that 7-OH is addictive.—
Jack Harvel,
Kansas City Star,
31 Mar. 2026
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Set in the heart of Midtown Manhattan, the grandiosity of MoMA is deceptive.—
Condé Nast,
Condé Nast Traveler,
30 Mar. 2026
Adjective
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The government took a genuine invitation to collaborate as a perfidious power grab.—
Gideon Lewis-Kraus,
New Yorker,
14 Mar. 2026
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For those trying to read Iran’s future, the lesson of 1953 is not just that foreign powers can be perfidious.—
Bobby Ghosh,
Time,
5 Mar. 2026
Adjective
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Nevada County’s admission comes as AI programs are under close watch around the globe for introducing incorrect legal references in cases, yet also increasingly offered as tools to help lawyers and judges research and write their briefs, motions and opinions.—
Sharon Bernstein,
Sacbee.com,
1 Apr. 2026
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Gemini 3 Pro invented elaborate technical justifications for marking incorrect answers as correct, reasoning that doing so would bring the peer’s score above the shutdown threshold.—
Jeremy Kahn,
Fortune,
1 Apr. 2026
Adjective
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If that doesn't open your eyes in law enforcement, something's wrong with you.—
Lauren Clark,
CBS News,
29 Mar. 2026
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Both assumptions are increasingly wrong.—
Brian Barlow,
Fortune,
28 Mar. 2026
Cite this Entry
“Insidious.” Merriam-Webster.com Thesaurus, Merriam-Webster, https://www.merriam-webster.com/thesaurus/insidious. Accessed 3 Apr. 2026.
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